The present invention relates to a waste toner container detector which detects when the container is full of waste toner collected from the photoreceptor.
Conventionally, a waste toner container is detected as being full by a weight sensor, a pressure sensor or an optical sensor provided in the waste toner container. Since the volume and weight of the waste toner tend to vary depending upon the waste toner density, however, detection by a weight or pressure sensor is not accurate. Detection by the optical sensor can also be inaccurate when the sensing surface of the sensor is soiled. In addition, any of the above waste toner container detectors is expensive.